Manufacturing method for an annular member and a pronged annular member

ABSTRACT

A workpiece 20 b  is formed that includes a circular bottom portion 22 b  having a hole 23 b  and an inner wall portion 24 b  around the hole 23 b , and a skirt-shaped outer wall portion 25 b  that includes prong portions 26 b  on the outer circumference of the bottom portion 22 b  and linking portions 27 b  that link these prong portions 26 b , and by cutting off the linking portions 27 b  and the portion that includes the inner wall portion 24 b  from the formed workpiece, a pronged annular member that includes the circular bottom portion 22 b  that has a hole 23 b  and the prong portions 26 b  on the outer circumference of the bottom portion 22 b.

TECHNICAL FIELD

The present invention relates to a manufacturing method for an annular member and a pronged annular member, and in particular, relates to a manufacturing method for an annular member in which an annular-shaped annular portion and a pronged annular member that has at least one prong formed substantially perpendicular on the outer circumference of this annular portion are manufactured, and a pronged annular member.

BACKGROUND ART

Conventionally a manufacturing method for this type of annular member has been proposed in which a carrier that is used in the planetary gear mechanism is manufactured by a press process and a bending process being applied to a cylindrical base material at room temperature. In this method, a discoid workpiece that includes a central portion, four prongs that extend radially from this center portion, and linking portions that link these prongs together is formed by applying a press process to a cylindrical base material to remove the linking portions from this workpiece and to form thereby a carrier in which the four prongs are bent at 90°.

In addition, a manufacturing method for this type of annular member has been proposed (for example, refer to Patent Document 1) that includes a roughly shaped piece formation step that forms a pronged roughly shaped piece that includes a base portion, a plurality of prong portions having differing widths (thicknesses) along the outer circumferential surface of one surface side of the base portion, and a film portion that extends between each of the prongs, and a trimming step in which the film portions of the roughly shaped piece and the center portion of the bottom portion formed by the roughly shaped piece formation step are trimmed. In this manufacturing method, during the roughly shaped piece formation step, backward extrusion formation is carried out such that the thickness of the film portion adjacent to a prong portion, whose width is narrower than the other prong portions, becomes thicker than the film portion between the other prong portions. Thereby, the induction of the material flow to the prong portions having a narrow width is promoted, and prong portions having differing widths and a uniform height are formed.

Patent Document 1: Japanese Patent Application Publication No. 2001-105085

DISCLOSURE OF THE INVENTION

In the former manufacturing method for an annular member described above, because it is necessary to provide a significant bending process to bend the four prong portions by 90° after the press process for the workpiece by a large elastic deformation of the base material, it is necessary to carry out annealing between the press process and the bending process, and this requires time from the initial press process of the base material to the completion of the carrier. In addition, in the latter manufacturing method for an annular member described above, because the material only flows in the circumferential direction of the discoid blank when backward extrusion formation is carried out, it is necessary to apply a comparatively heavy load to the discoid blank when carrying out the backward extrusion formation.

It is an object of the manufacturing method for an annular member of present invention to reduce the manufacturing steps for manufacturing the annular member from the base material. In addition, it is an object of the manufacturing method for an annular member of the present invention to manufacture an annular member from the base material without carrying out annealing. Furthermore, it is an object of the manufacturing method for an annular member of the present invention to shorten the time that is necessary to manufacture the annular member from the base material. It is an object of the manufacturing method for an annular member of the present invention to reduce the load required when carrying out the press process on the base material.

The manufacturing method for an annular member of the present invention includes the following means for attaining at least a portion of the objects described above.

The manufacturing method for an annular member of the present invention manufactures a pronged annular member that includes an annular-shaped annular portion and at least one prong formed substantially perpendicular on the outer circumference of this annular portion, includes:

(a) preparing an annular base material;

(b) forming a workpiece by applying one press process to this base material, the workpiece including a circular bottom portion having a hole in the center thereof and a skirt-shaped outer wall portion that includes prong portions that form the prongs on the outer circumference of the bottom portion and linking portions that link the prong portions; and

(c) forming the pronged annular member by removing the linking portions from the formed workpiece.

In the manufacturing method for an annular member of the present invention, a workpiece is formed by applying one press process to a prepared annular base material, the workpiece including a circular bottom portion having a hole in the center thereof and a skirt-shaped outer wall portion that includes prong portions on the outer circumference of the bottom portion and linking portions that link the prong portions, and the linking portions are removed from the formed workpiece to form the pronged annular member. Therefore, it is not necessary to carry out a bending process on the prong portions. As a result, it is possible to decrease the manufacturing steps for manufacturing the annular member from the annular base material, and additionally, it is possible to decrease the time that is necessary to manufacture the annular member from the base material. In addition, in the case in which a workpiece is formed by one press process on the annular material and has a cylindrical vertical wall portion that is concentric to the outer wall portion along the hole in the center of the bottom portion, it is possible to increase the directions of the flow of the base material (substance), and it is possible to reduce further the load (pressure) that is necessary when carrying out the press process on the base material.

The manufacturing method for such an annular member of the present invention can be characterized in that at least the steps (b) described above and after can be carried out by cold forging. Thereby, because heating is not necessary, it is possible to shorten the time that is necessary for cooling.

In addition, the manufacturing method for an annular member of the present invention can be characterized in that at least none of the steps (b) described above and after carry out annealing. Thereby, it is possible to manufacture the annular member from the base material without carrying out annealing. As a result, the annealing step and the cooling step that follows the annealing are not necessary, and it is possible to shorten the time that is necessary to manufacture the annular member from the base material.

Furthermore, in the manufacturing method for an annular member of the present invention, the step (b) described above is a step in which the workpiece is formed such that the outer diameter of the linking portions in the outer wall portion is larger than the outer diameter of the prong portions, and step (c) described above can be a step that includes a step (c1), in which the linking portions are removed such that the linking portions in the outer wall portion are sheared off by a force that acts from the prong portions toward the prongs. Thereby, it is possible to remove the linking portions readily. In this case, the step (b) described above can be a step in which the workpiece described above is formed such that the inner diameter of the linking portions in the outer wall portion is larger than the inner diameter of the prong portions. In addition, the step (b) described above can be a step in which the workpiece is formed such that the inner diameter of the linking portions in the outer wall portion is substantially identical to the outer diameter of the prong portions. Furthermore, the step (c) described above can be a step in which the linking portions are removed, and at the same time, the portion of the workpiece that includes the hole in the bottom portion is cut off. Thereby, in comparison to carrying out the step of removing the linking portions and the step of cutting off the portion that includes the hole in the bottom of the workpiece as separate steps, it is possible to reduce the number of steps, and it is possible to shorten the time that is necessary to manufacture the annular member from the base material.

Alternatively, in the manufacturing method for an annular member of the present invention, the step (b) described above can be a step in which the workpiece described above is formed such that the wall thickness of the connecting portions, which are the portions that connect the prong portions and the linking portions, is thinner than the wall thickness of the prong portions and the wall thickness of the linking portions. Thereby, in the case in which the linking portions are removed by applying a force to the portions that include the connecting portions (for example, the base of a linking portion at the bottom portion and a connecting portion), it is possible to reduce further the load that is necessary to remove the linking portions.

In the manufacturing method for an annular member of the present invention, the step (b) described above can be a step in which the workpiece is manufactured such that the wall thickness of the linking portions is thinner than the wall thickness of the prong portions. Thereby, in comparison to making the wall thickness of the linking portions and the wall thickness of the prong portions substantially identical, it is possible to reduce the amount of base material that flows toward the linking portion side when carrying out the press process. As a result, it is possible to reduce the waste of material up to the point at which the annular member has been manufactured from the base material. In addition, the step (b) described above can be a step in which the workpiece is formed such that the base of the inside of the prong portions at the bottom portion has a wall thickness that has a radius that is larger in comparison to the base of the inside of the connecting portions at the base portion. Thus, it is possible to increase the strength of the base of the prong portions, and at the same time, it is possible to suppress cracks from occurring in the base of the prong portions while being elastically deformed due to the press process.

In addition, in the manufacturing method for the annular member of the present invention, the step (c) described above can be a step that includes a step (c2), in which the inner diameter of the prong portions is widened after removing the linking portions from the formed workpiece, and step (c) described above can be a step that includes a step (c3) in which the trimming of the locations that link the prong portions and the linking portions is carried out after removing the linking portions from the formed workpiece.

In the manufacturing method for an annular member of the present invention, the step (c) described above can be a step that includes a step (c4), in which at least one of the roughness and the evenness of the surface of at least the inside of the bottom portion are adjusted after the linking portions are removed from the formed workpiece. In this case, the step (a) described above can be a step in which a base material is prepared whose surface has been subject to a phosphating treatment providing a surface coating that includes a metallic soap, and step (c4) described above can be a step in which at least one of the roughness and evenness of this surface is adjusted after providing a process in which the metallic soap is removed. Thereby, it is possible to adjust the roughness and the evenness of the surface of the inside of the bottom portion.

In addition, in the manufacturing method for an annular member of the present invention, the step (b) described above can be a step in which the workpiece is formed having a cylindrical vertical wall that is concentric to the outer wall portion along the hole in the center of the bottom portion. Thereby, it is possible to increase the directions of the flow of the base material when carrying out the press process one time, and it is possible to reduce further the load that is necessary when carrying out the press process on the base material.

In the manufacturing method for an annular member of the present invention that is a mode in which a workpiece is formed that has these vertical wall portions, the step (b) described above can be a step in which the workpiece is formed such that the length to the end portion of this vertical wall portion is adjusted by varying the wall thickness of the linking portions depending on the distance from the prong portions. Thereby, it is possible to adjust the length to the end portion of the vertical wall portion. In this case, the step (b) described above can be a step in which the workpiece is formed such that the wall thickness of the linking portions becomes continuously larger as the distance from the prong portions becomes larger. In addition, the step (b) described above can be a step in which the workpiece is formed such that the end portion of the vertical wall member becomes continuous along the circumference of the vertical wall portion.

In addition, in the manufacturing method for an annular member of the present invention that is a mode in which a workpiece is formed that has a vertical wall portion, the step (b) described above can be a step in which the workpiece is formed such that the inner circumferential surface of the vertical wall portion has a predetermined shape. In this case, the step (b) can be a step in which the workpiece is formed such that this predetermined shape is a spline shape. Thereby, the base material readily flows toward the vertical wall portion side when the press process is carried out, and it is possible to reduce further the load that is necessary when carrying out, the press process on the base material.

Furthermore, in the manufacturing method for an annular member of the present invention that is a mode in which a workpiece is formed that has a vertical wall portion, the step (b) described above can be a step in which the workpiece that is formed has vertical wall portions that include a first vertical wall portion having a direction that is identical to the direction of the outer wall portion with respect to the hole in the center of the bottom portion and a second vertical wall portion having a direction that is opposed to the direction of the outer wall portion with respect to the hole in the center of the bottom portion. In this case, the step (c) described above can be a step that includes a step (c5) in which the first vertical wall portion is removed from the workpiece after the linking portions have been removed from the formed workpiece.

In the manufacturing method for an annular member of the present invention, the annular member is a carrier in a planetary gear mechanism. Note that in addition to such a carrier, any type of annular member is satisfactory when the annular member is a pronged annular member that includes an annular-shaped annular portion and at least one prong formed substantially perpendicular on the outer circumference of the annular-shaped annular portion.

In the pronged annular member of the present invention including an annular-shaped annular portion and at least one prong that is formed substantially perpendicular on the outer circumference of the annular portion, generally,

the pronged annular member is formed by removing the linking portions from a workpiece that has been formed by one press process being applied to an annular base material, the workpiece including a circular bottom portion having a hole in the center thereof and a skirt-shaped outer wall portion that includes prong portions that form prongs on the outer circumference of the bottom portion and linking portions that link these prong portions.

The pronged annular member of the present invention is formed by removing the linking portions from the workpiece that has been formed by one press process being applied to an annular base material, the workpiece including a circular bottom portion having a hole in the center thereof and a skirt-shaped outer wall portion that includes prong portions in which prongs are formed on the outer circumference of the bottom portion and linking portions that link these prong portions. Therefore, in contrast to carrying out a bending process at the prong portions, it is possible to manufacture a pronged annular member from an annular member by using fewer manufacturing steps, and it is possible to shorten the time that is necessary to manufacture the pronged annular member from the base material.

In such a pronged annular member of the present invention, the workpiece can be formed such that the outer diameter of the linking portions in the outer wall portion is larger than the outer diameter of the prong portions, and the pronged annular member can be formed by removing the linking portions such that the linking portions in the outer wall portions are sheared off from the prong portions by a force that is applied in the direction of the prongs. In this case, the workpiece can be formed such that the inner diameter of the linking portions in the outer wall portion is larger than the inner diameter of the prong portions. In addition, the workpiece can be formed such that the inner diameter of the linking portions in the outer wall portion is substantially identical to the outer diameter of the prong portions.

In addition, in the pronged annular member of the present invention, the pronged annular member can be formed by removing the linking portions and by cutting off a portion of the workpiece that includes the hole in the bottom portion. In addition, the workpiece can be formed such that the wall thickness of the connecting portions, which are the parts that connect the prong portions and the linking portions, is made thinner than the wall thickness of the prong portions and the wall thickness of the linking portions.

Furthermore, in the pronged annular member of the present invention, the workpiece can be formed such that the wall thickness of the linking portions is made thinner than the wall thickness of the prong portions. In addition, the workpiece can be formed such that the base of the inside of the prong portions at the bottom portion has a wall thickness that has a radius that is larger in comparison to the base of the inside of the linking portions at the bottom portion.

Alternatively, in the pronged annular member of the present invention, the pronged annular member can be formed by widening the inner diameter of the prong portions after removing the linking portions from the formed workpiece. In addition, the pronged annular member can be formed by carrying out trimming of the locations that link the linking portions and the prong portions after removing the linking portions from the formed workpiece.

In the pronged annular member of the present invention, the pronged annular member can be formed by adjusting at least one of the roughness and the evenness of at least the inside surface of the bottom portion after removing the linking portions from the formed workpiece. In this case, the annular base material can be a base material whose surface has been subject to a phosphating treatment that provides a surface coating that includes a metallic soap, and the pronged annular member can be formed by adjusting at least one of the roughness and the evenness of this surface after providing a process in which the metallic soap is removed.

In addition, in the pronged annular member of the present invention, the workpiece can be a member having a cylindrical vertical wall portion that is concentric to the outer wall portion along the hole in the center of the bottom portion.

In the manufacturing method for an annular member of the present invention that is a mode in which the workpiece has a vertical wall portion, the workpiece can be formed by adjusting the length to the end portion of the vertical wall portion by varying the wall thickness of the linking portions according to the distance from the prong portions. In this case, the workpiece can be formed such that the wall thickness of the linking portions becomes continuously larger as the distance from the prong portions becomes larger.

In addition, in the pronged annular member of the present invention that is a mode in which the workpiece has a vertical wall portion, the workpiece is formed such that the inner circumferential surface of the vertical wall portion has a predetermined shape. In this case, the workpiece can be formed such that the inner circumferential surface of the vertical wall portion is a spline shape.

Furthermore, in the pronged annular member of the present invention that is a mode in which the workpiece has vertical wall portions, the workpiece can be formed such that the vertical wall portions include a first vertical wall portion having a direction that is identical to that of the outer wall portion with respect to the hole in the center of the bottom portion and a second vertical wall portion that has a direction that is opposed to that of the outer wall portion with respect to the hole in the center of the bottom portion. In this case, the pronged annular member can be formed by removing the first vertical wall portion from the workpiece after removing the linking portions from the formed workpiece.

In the pronged annular member of the present invention, the pronged annular member can be a carrier in a planetary gear mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the external appearance of a carrier 20.

FIG. 2 is an AA perspective view in which the carrier 20 in FIG. 1 is viewed from the A-A plane.

FIG. 3 is a step diagram showing an example of a mode of the manufacturing of the carrier 20.

FIG. 4 is a perspective view showing the external appearance of a base material 20 a.

FIG. 5 is a perspective view showing the external appearance of a workpiece 20 b.

FIG. 6 is an AA perspective view in which the workpiece 20 b in FIG. 5 is viewed from the A-A plane.

FIG. 7 is a BB perspective view in which the workpiece 20 b in FIG. 5 is viewed from the B-B plane.

FIG. 8 is a cross-sectional view of a process apparatus 40.

FIG. 9 is an AA perspective view in which the process apparatus 40 in FIG. 8 is viewed from the A-A plane.

FIG. 10 is a BB perspective view in which the process apparatus 40 in FIG. 8 is viewed from the B-B plane.

FIG. 11 is a cross-sectional view of the process apparatus 40 when the workpiece 20 b is being formed from the base material 20 a.

FIG. 12 is a cross-sectional view of the E-E cross-section of the process apparatus 40 in FIG. 11.

FIG. 13 is a perspective view showing the external appearance of a pronged annular member 20 c.

FIG. 14 is an AA perspective view in which the workpiece 20 c in FIG. 13 is viewed from the A-A plane.

FIG. 15 is a BB perspective view in which the workpiece 20 c in FIG. 13 is viewed from the B-B plane.

FIG. 16 is a cross-sectional view of a shearing apparatus 60.

FIG. 17 is an AA perspective view in which the shearing apparatus 60 in FIG. 16 is viewed from the A-A plane.

FIG. 18 is a BB perspective view showing the B-B plane of the shearing apparatus 60 in FIG. 16.

FIG. 19 is an explanatory drawing showing a mode when the portion that includes the linking portions 27 and the inner wall portion 24 are cut off of the workpiece 20 b by using the shearing apparatus 60.

FIG. 20 is a cross-sectional view of the E-E cross-section of the shearing apparatus 60 in FIG. 19.

FIG. 21 is an explanatory drawing showing a mode in which the inner diameter of the prong portions 26 b of the pronged annular member 20 c is widened.

FIG. 22 is an explanatory drawing showing a portion where the trimming of the pronged annular member 20 c is carried out.

FIG. 23 is an explanatory drawing showing a portion where the coining of the pronged annular member 20 c is carried out.

FIG. 24 is a step diagram showing an example of a mode of the manufacture of a modified example of a carrier 20.

FIG. 25 is a perspective view showing the external appearance of the pronged annular member 20 d with an inner wall portion.

FIG. 26 is an explanatory drawing showing an example of the bottom side 50 b of a modified example of the process apparatus 40B.

FIG. 27 is a perspective view showing the external appearance of the workpiece 120 b.

FIG. 28 is an AA perspective view in which the workpiece 120 b in FIG. 27 is viewed from the A-A plane.

FIG. 29 is a BB perspective view in which the workpiece 120 b in FIG. 27 is viewed from the B-B plane.

FIG. 30 is a perspective view showing the external appearance of the workpiece 220 b.

FIG. 31 is an AA perspective view in which the workpiece 220 b in FIG. 30 is viewed from the A-A plane.

FIG. 32 is a BB perspective view in which the workpiece 220 b in FIG. 30 is viewed from the B-B plane.

BEST MODES FOR CARRYING OUT THE INVENTION

Next, a preferred mode for implementing the present invention will be explained by using embodiments.

FIG. 1 is a perspective view showing as an embodiment of the present invention the external appearance of the carrier 20 that has been manufactured by the manufacturing method for an annular member, and FIG. 2 is an AA perspective view in which the carrier 20 in FIG. 1 is viewed from the A-A plane. As shown in FIG. 1 and FIG. 2, the carrier 20 that is manufactured by the manufacturing method of this embodiment is structured by an annular bottom portion 22 that has a hole 23 formed in the center thereof, prong portions 26 that include four prongs that are formed on the outer circumference of the bottom portion 22 substantially perpendicular to the bottom portion 22, and a boss portion 28 that is formed as a hollow shaft on the side of the bottom portion 22 that is opposed to the prong portions 26.

The carrier 20 having such an embodiment is manufactured as follows. FIG. 3 is a step diagram showing a mode by which the carrier 20 of the embodiment is manufactured. The manufacture of the carrier 20 first starts from a step in which the annular base material 20 a illustrated in FIG. 4 is prepared (step S100). As shown in FIG. 4, the base material 20 a is formed as an annular member that has an inner diameter R1 and outer diameter R2. This base material 20 a is manufactured specifically by preparing a rod of a material that can be cold forged (for example, a low carbon steel, a low carbon steel alloy, aluminum, an aluminum alloy, copper, a copper alloy, or the like) (step S110); forming an annular member having a hole in the center thereof by subjecting the prepared rod to hot forging, warm forging, or cold forging (step S120); carrying out a dehardening process on the formed annular member (step S130); carrying out shot blasting in order to eliminate scales on the surface of the annular member (step S140); carrying out C-surface machining (beveling) and width machining in order to shape the profile of the annular member (step S150, S160); and providing a phosphating treatment (step S170). Here, the phosphating treatment is a process that forms a chemical conversion coating (for example, a phosphate coating) on the surface of the annular member in order to minimize the frictional resistance between the process apparatus and the base material 20 a when a press process is carried out (described below), and the surface of the formed chemical conversion layer is coated by a metallic soap or the like. Note that because the step in which the base material 20 a is prepared is not essential to the present invention, any further detailed explanation thereof will be omitted.

When such a base material 20 a has been prepared, next, a workpiece 20 b, which is illustrated in FIG. 5 to FIG. 7, is formed by one press process being applied to the prepared annular base material 20 a (step S200). FIG. 5 is a perspective view of the external appearance of the workpiece 20 b, FIG. 6 is an AA perspective view in which the workpiece 20 b in FIG. 5 is viewed from the A-A plane, and FIG. 7 is a cross-sectional view showing the B-B cross-section of the workpiece 20 b in FIG. 5. As shown in FIG. 5 to FIG. 7, the workpiece 20 b includes a circular bottom portion 22 b, an outer wall portion 25 b, and a boss portion 28 b. The circular bottom portion 22 b, which has an outer diameter R6, has in the center thereof a hole 23 b having a diameter R3 and a substantially cylindrical inner wall portion 24 b, which is around the hole 23 b, having an inner diameter R3 and an outer diameter R4. The outer wall portion 25 b includes prong portions 26 b that have an inner diameter R5 and an outer diameter R6 and are formed on the outer circumference of the bottom portion 22 b substantially perpendicular to the bottom portion 22 b on the same side as the inner wall portion 24 b with respect to the bottom portion 22 b. The outer wall portion 25 b also includes linking portions 27 b that are linked to the side surface of the bottom portion 22 b and the prong portions 26 b, and have an inner diameter R7 that is substantially identical to the outer diameter R6 of the bottom portion 22 b and an outer diameter R8. The boss portion 28 b is formed as a hollow shaft-shaped cylinder on the side of the bottom portion 22 b that is opposed to the outer wall portion 25 b and has an inner diameter R9 that is slightly larger than the inner diameter R3 of the inner wall portion 24 b and an outer diameter R10 that is smaller than the outer diameter R6 of the bottom portion 22 b. Here, the thickness of the pronged portion 26 b is formed so as to be thicker (the thickness is large) than the thickness D2 ((R8-R7)/2) of the linking portions 27 b. In addition, in the embodiment, the portions that connect the prong portions 26 b and the linking portions 27 b in the outer wall portion 25 b are referred to as connecting portions 29 b. The thickness D4 of these connecting portions 29 b is formed so as to be thinner than the thickness D1 of the prong portions 26 b and the thickness D2 of the linking portions 27 b. In the embodiment, the steps by which the workpiece 20 b is formed are carried out by using the process apparatus 40 that is illustrated in FIG. 8. FIG. 8 is a cross-sectional view of the process apparatus 40, FIG. 9 is an AA perspective view in which the process apparatus 40 in FIG. 8 is viewed from the A-A plane, and FIG. 10 is a BB perspective view in which the process apparatus 40 in FIG. 8 is viewed from the B-B plane. Note that the cross-section of the process apparatus 40 in FIG. 8 corresponds to the C-C cross-section of the process apparatus 40 in FIG. 9 and the D-D cross-section of the process apparatus 40 in FIG. 10. The process apparatus 40 is structured by an upper die 41 that is disposed on the upper portion inside the process apparatus 40 and a lower die 50 that is disposed below and concentric to the upper die 41. The upper die 41 includes, for example, an upper die mandrel 42 and an upper die punch 43 (refer to FIG. 9). The upper die mandrel 42 is disposed at the center bottom portion inside the upper die 41 and is formed in a cylindrical shape having an outer diameter R11 that is smaller than the inner diameter R1 of the base material 20 a and substantially identical to the outer diameter R4 of the inner wall portion 24 b of the workpiece 20 b. The upper die punch 43 is formed as a hollow shaft such that the inner circumferential surface is in contact with the outer circumferential surface of the upper die mandrel 42 and the lower end portion of the outer circumferential surface thereof is formed into a shape that alternates between the portions of a circle having an outer diameter R12 that is substantially identical to the inner diameter R5 of the prong portions 26 b of the workpiece 20 b and the portions of a circle having an outer diameter R13 that is substantially identical to the inner diameter R7 of the linking portions 27 b. The lower die 50 includes, for example, a lower die mandrel 51, a lower-die punch 52, a first die 53 (refer to FIG. 10), and a second die 54. The lower die mandrel 51 is disposed on the upper center portion in the lower die 50, the upper end portion thereof is formed as a circle having an outer diameter R14 that is substantially identical to the outer diameter (the inner diameter of the inner wall portion 24 b ) R3 of the hole 23 b of the workpiece 20 b. In addition, the lower die mandrel 51 is formed such that the outer diameter increases stepwise from a position that is a length L1 from the upper end portion downward to the outer diameter R17 that is substantially identical to the inner diameter R9 of the boss portion 28 b of the workpiece 20 b. The lower die punch 52 is formed as a hollow shaft having an inner diameter R17, and is formed in a cylindrical shape having an outer diameter R18 that is substantially identical to the outer diameter R10 of the boss portion 28 b of the workpiece 20 b. The lower die punch 52 is for mounting the base material 20 a. The first die 53 is formed as a hollow shaft such that the inner circumferential surface thereof is in contact with the outer circumferential surface of the lower die punch 52 and the outer circumference thereof is formed into a shape that alternates between the portions of a circle having an outer diameter R15 that is substantially identical to the outer diameter R6 of the bottom portion 22 b of the workpiece 20 b and the portions of a circle having an outer diameter R16 that is substantially identical to the outer diameter R8 of the linking portions 27 b. The second die 54 is formed as a hollow shaft-shaped cylinder such that the inner circumferential surface thereof is in contact with the outer circumferential surface of the first die 53. Here, the lower die punch 52 is formed so as to be able to move in a vertical direction. In addition, the first die 53 is disposed such that the upper end portion thereof is at a position that is lower than the upper end portion of the second die 54 by a length L2, and on the outer circumference, the portions that are formed having an outer diameter R15 are opposed to the portions of the upper die punch 43 that are formed having an outer diameter R12, and the portions that are formed having an outer diameter R16 are opposed to the portions of the upper die punch 43 formed having an outer diameter R13.

FIG. 11 is an explanatory drawing for explaining a mode when the workpiece 20 b is formed by using the process apparatus 40, and FIG. 12 is a cross-sectional view of the E-E cross-section of the process apparatus 40 in FIG. 11. Here, the cross-section of the process apparatus 40 at the upper right side portion in FIG. 11 corresponds to the F-F cross-section of the process apparatus 40 in FIG. 12. The cross-section of the process apparatus 40 in the lower right side portion in FIG. 11 further enlarges the cross-section of the upper right side portion of the process apparatus 40. When the workpiece 20 b is formed from the base material 20 a, first the annular base material 20 a is mounted on the upper portion of the upper end portion of the lower die punch 52 so as to be concentric to the lower die mandrel 51. Then in this state, the upper die 41 is lowered. At this time, the upper die punch 43 abuts the base material 20 a, and it is lowered further while pressing down on the base material 20 a and the lower die punch 52. The upper die mandrel 42 stops descending when the lower end portion thereof abuts the upper end portion of the lower die mandrel 51. Then, while the upper end portion of the lower die punch 43 deforms the base material 20 a up to a predetermined position that is lower than the upper end portion of the first die 53, the upper die 41 is lowered. At the point in time that the upper die 41 stops descending, the base material 20 a has been formed into a shape that is formed by the upper die punch 43, the lower die mandrel 51, the lower die punch 52, the first die 53, and the second die 54, or specifically, the base material layer 20 a is formed into the shape of the workpiece 20 b shown in FIG. 5 to FIG. 7. Here, as described above, the thickness D1 of the prong portions 26 b of the outer wall portion 25 b of the workpiece 20 b is formed so as to have a wall thickness larger than the thickness D2 of the linking portions 27 b. Thus, the strength of the base of the prong portions 26 b at the bottom portion 22 b is ensured, and at the same time, it is possible to suppress breakage of the workpiece 20 b due to cracks occurring in the base of the prong portions 26 b at the bottom portion 22 b during elastic deformation. Furthermore, by forming the thickness D1 of the prong portions 26 b so as to have a wall thickness larger than the thickness D2 of the linking portions 27 b, in comparison to forming the thickness D1 and the thickness D2 so as to be substantially identical, it is possible to minimize the amount of the base material (material) that flows toward the linking portions 27 b side during the press process. As will be described below, because these linking portions 27 b are cut off, it is possible to reduce the waste of the material by minimizing the amount of the base material that flows to the linking portions 27 b side. In addition, in the case in which the workpiece 20 b is formed by using this process apparatus 40, in addition to the outer wall portion 25 b formed by the upper die punch 43 and the second die 54 and the boss portion 28 b formed by the lower die mandrel 51, the lower die punch 52, and the first die 53, the substantially cylindrical inner wall portion 24 b is formed by the lower die mandrel 51 and the upper punch 43. Thus, it is possible to increase the flow directions of the base material 20 a during the press process, and it is possible to minimize the pressure that is necessary to form the workpiece 20 b from the base material 20 a. Thereby, it is possible to form the workpiece 20 b from the base material 20 a by cold forging. As a result, there is no need to heat the base material 20 a as is done in a method that carries out hot forging, and it is possible to shorten the time necessary for cooling. In addition, because the temperature change is small in comparison to a method in which hot forging is carried out, it is possible to carry out the elastic deformation with a higher precision. Note that when forming the workpiece 20 b by using the process apparatus 40, the sum of the thickness D3 of the bottom portion 22 b of the workpiece 20 b and the height L3 of the prong portions 26 b (the height of the linking portions 27 b ) is formed so as to be smaller than the length L2 between the upper end portion of the first die 53 and the upper end portion of the second die 54.

When the workpiece 20 b is formed in this manner, the linking portions 27 b are cut off of the formed workpiece 20 b to form the pronged annular member 20 c that is illustrated in FIG. 13 to FIG. 15 (step 310), and at the same time, the formed pronged annular member 20 c is subject to (step S300) a finishing process (step 320 to step 350) to complete thereby the carrier 30 described above. FIG. 13 is a perspective view of the external appearance of the pronged annular member 20 c, FIG. 14 is an AA perspective view in which the pronged annular member 20 c in FIG. 13 is viewed from the A-A plane, and FIG. 15 is a BB perspective view in which the pronged angular member 20 c in FIG. 13 is viewed from the B-B plane. As shown in FIG. 13 to FIG. 15, the pronged annular member 20 c includes a circular bottom portion 22, prong portions 26 c, and a boss portion 28 c. The circular bottom portion 22 has in the center thereof a hole 23 c that has an outer diameter R19, which is slightly larger than the outer diameter R4 of the inner wall portion 24 b of the workpiece 20 b. The prong portions 26 c includes 4 prongs having an inner diameter R5 and an outer diameter R6 that are formed on the outer circumference of the bottom portion 22 substantially perpendicular to the bottom portion 22. The boss portion 28 c is formed as a hollow shaft-shaped cylinder having an inner diameter R19 and an outer diameter R10 on the side of the bottom portion 22 c that is opposed to the prong portions 26 c.

In this embodiment, such a pronged annular member 20 c is formed by using the shearing apparatus 60. FIG. 16 is a cross-sectional view of the shearing apparatus 60, FIG. 17 is an AA perspective view in which the shearing apparatus 60 in FIG. 16 is viewed from the A-A plane, and FIG. 18 is a BB perspective view in which the shearing apparatus 60 in FIG. 16 is viewed from the B-B plane. Note that the cross-section of the shearing apparatus 60 in FIG. 16 corresponds in the C-C cross-section of the shearing apparatus 60 in FIG. 17 and to the D-D cross-section of the shearing apparatus 60 in FIG. 18. As shown in the figures, the shearing apparatus 60 is structured by an upper die 61 that is disposed on the upper portion inside the shearing apparatus 60 and a lower die 65 that is disposed below and concentric to the upper die 61. The upper die 61 is disposed at the center bottom portion of the upper die 61 and the convex inner circumferential surface of the bottom end portion is formed in a circular shape having an inner diameter R20 that is slightly larger than the outer diameter R19 of the hole 23 c of the pronged annular member 20 c. The upper die 61 includes, for example, an upper die punch 62 (refer to FIG. 17) in which the outer circumference is formed into a shape that alternates between the portions of a circle having an outer diameter R21 that are substantially identical to the inner diameter R5 of the prong portions 26 c of the pronged annular member 20 c and the portions of a circle having an outer diameter R22 that are substantially identical to the outer diameter R6 of the bottom portion 22 c (the inner diameter R7 of the linking portions 27 b of the workpiece 20 b ). The lower die 65 includes, for example, a mandrel 66, a lower die punch 67, and a die 68. The mandrel 66 is disposed at the upper center portion inside the lower die 65 and is formed in a cylindrical shape having an outer diameter R23 that is substantially identical to the outer diameter R19 of the hole 23 c of the pronged annular member 20 c. The lower punch 67 has an inner circumferential surface that is in contact with the outer circumferential surface of the mandrel 66 and the outer circumference is formed into a shape that alternates between the portions of a circle having an outer diameter R24 that is substantially identical to the outer diameter R6 of the bottom portion 22 c of the pronged annular member 20 c and the portions of a circle having a diameter R25 which is slightly larger than the outer diameter R24. The upper end portion thereof is formed into a shape that allows the workpiece 20 b to be mounted thereon. The die 68 is formed into a hollow shaft-shaped cylinder such that the inner circumferential surface thereof is in contact with the outer circumferential surface of the lower die punch 67. Here, the lower side punch 67 is formed so as to be able to move in a vertical direction, and on the outer circumference thereof, is disposed such that the portions that are formed having an outer diameter R24 are opposed to the portions of the upper die punch 62 formed having an outer diameter R21, and the portions that are formed having an outer diameter R25 are opposed to the portions of the upper die punch 62 formed having an outer diameter R22. In addition, the die 68 is provided with an inclined portion in which the outer circumference inclines in a radially outward direction on the upper end portion of the portions that are formed having an inner diameter R25. FIG. 19 is an explanatory drawing showing a mode when the linking portions 27 and the portion that includes the inner wall portion 24 are cut off of the workpiece 20 b by using the shearing apparatus 60, and FIG. 20 is a cross-sectional view showing the E-E cross-section of an enlarged drawing of the shearing apparatus 60 in FIG. 19. Note that the cross-section of the shearing apparatus 60 in FIG. 19 corresponds to the F-F cross-section in FIG. 20. When the linking portions 27 b and the portion that includes the inner wall portion 24 b are cut off of the workpiece 20 b, first the workpiece 20 b is mounted on the upper portion of the upper end portion of the lower side punch 67 so as to be concentric to the mandrel 66 and such that the prong portions 26 c of the workpiece 20 b are opposed to the portions of the lower die punch 67 formed having an outer diameter R24 and the linking portions 27 b are opposed to the portions of the lower die punch 67 formed having an outer diameter R25. Then, in this state, the upper die 61 is lowered. At this time, when the upper die punch 62 abuts the bottom portion 22 b of the workpiece 20 b, the upper die 61 is further lowered while pressing down on the workpiece 20 b and the lower die punch 67. Then, as shown in FIG. 19 and FIG. 20, when the upper die 61 is lowered further, the portions that include the inner wall portion 24 b of the workpiece 20 b are cut off due to the shearing force by the inside of the lower end portion of the upper die punch 62 and the outside of the upper end portion of the mandrel 66, and the linking portions 27 b are cut off due to the shearing force of the portions of the outside of the lower end portion of the upper die punch 62 formed having an outer diameter R22 and the portions of the inside of the upper end portion of the die 67 formed having an outer diameter R25 being applied to the base of the linking portions 27 b at the bottom portion 22 b and the connecting portions 29 b. Specifically, while the workpiece 20 b is being pressed downward by the upper die punch 62 in a state in which the bottom portion 22 b is abutting the upper die punch 62, the portion that includes the inner wall portion 24 b is cut off of the boss portion 28 b side of the workpiece 20 b, and at the same time, the linking portions 27 b are cut off of the boss portion 28 b side (the base side of the linking portions 26 b at the bottom portion 22 b ). By cutting off the linking portions 27 b in this manner, it is possible to cut off the linking portions 27 b easily. Here, when the linking portions 27 b are cut off of the workpiece 20 b, as has been described above, the workpiece 20 b is formed such that the thickness D1 of the prong portions 26 b is more thick than the thickness D2 of the linking portions 27 b, and thus the occurrence of cracks in the base of the prong portions 26 b at the bottom portion 22 b can be suppressed. In addition, because the workpiece 20 b is formed such that the thickness D4 of the connecting portions 29 b is thin in comparison to the thickness D1 of the prong portions 26 b and the thickness D2 of the linking portions 27 b, it is possible to reduce the load (pressure) that is necessary to cut the linking portions 27 b off of the workpiece 20 b in comparison to a method in which the thickness D4 of the connecting portions 29 b is substantially identical to the thickness D1 of the prong portions 26 b and the thickness D2 of the linking portions 27 b. Thus, a pronged annular member 20 c is formed that includes a circular bottom portion 22 c that has a hole 23 c in the center thereof, prong portions 26 c that include four prongs that are formed on the outer circumference of the bottom portion 22 c substantially perpendicular to the bottom portion 22 c, and a boss portion 28 c that is formed as a hollow shaft-shaped cylinder on the side of the bottom portion 22 c that is opposed to the prong portions 26 c.

The finishing process (steps S320 to S350) of the pronged annular member 20 c specifically includes a process (step S320), as shown in FIG. 21, in which the prong portions 26 c are widened outward (the direction of the arrow in the figure) such that inner diameter of the prong portions 26 c of the formed pronged annular member 20 c becomes larger; a process (step S330), as shown in FIG. 22, in which trimming of the cross-sections (the side surfaces of the prong portions 26 c ) is carried out where the linking portions 27 b were cut off when the pronged annular member 20 c was formed; a process (step S340) in which metallic soap that has been coated on the surface of the pronged annular member 20 c is removed; and a coining process (step S350), as shown in FIG. 23, in which the surface (inclined portion) of the bottom portion 22 c of the pronged annular member 20 c is smoothed.

In this manner, to simplify the explanation, the manufacturing method for the carrier 20 of the embodiment forms a workpiece 20 b by elastic deformation using one press process on a prepared base material 20 a, the workpiece being structured by a circular bottom portion 22 b having a hole 23 b in the center thereof and a skirt-shaped outer wall portion 25 b that includes the prong portions 26 b on the outer circumference of the bottom portion 22 b and the linking portions 27 b that link these prong portions 26 b. The carrier 20 is completed by removing the linking portions 27 b from the formed workpiece 20 b. As can be understood from the steps described above, in the steps for completing the carrier 20 from the base material 20 a, the elastic deformation is carried out only one time in the press process of step S200, and thus it is not necessary to carry out annealing for subsequent elastic deformation. Specifically, annealing is not necessary in the steps for completing the carrier 20 from the base material 20 a. Therefore, the time that is necessary in order to carry out an annealing step and a cooling step after annealing can be reduced, it is possible to reduce the steps for manufacturing the carrier 20 from the base material 20 a, and it is possible to reduce the time that is necessary to manufacture the carrier 20 from the base material 20 a.

According to the manufacturing method for the carrier 20 in the embodiment described above, a workpiece 20 b is formed by one press process carried out on a prepared annular base material 20 a, the workpiece being structured by a circular bottom portion 22 b that has a hole 23 b in the center thereof and a skirt shaped outer wall portion 25 b that includes prong portions 26 b on the outer circumference of the bottom portion 22 b and linking portions 27 b that link these prong portions 26 b. Because the carrier 20 is completed by removing the linking portions 27 b from the formed workpiece 20 b, it is not necessary to carry out annealing in the steps for completing the carrier 20 from the base material 20 a As a result, it is possible to reduce the steps for completing the carrier 20 from the base material 20 a, and it is possible to shorten the time for completing the carrier 20 from the base material 20 a. In addition, according to the manufacturing method for the carrier 20 of the embodiment, because the workpiece 20 a is formed from a base material 20 a by using cold forging, the time that is necessary to heat the base material 20 a, cool the formed workpiece 20 b, and the like becomes unnecessary. As a result, it is possible to shorten further the time for completing the carrier 20 from the base material 20 a.

In the manufacturing method for the carrier 20 of the embodiment, the linking portions 27 b and the portion that includes the inner wall portion 24 b are cut off simultaneously from the workpiece 20 b, but this need not be carried out simultaneously. An example of the manufacturing method for the carrier 20 in this case is shown in FIG. 24. Except for the point that step S400 is carried out instead of step S300 in the manufacturing steps in FIG. 3, the manufacturing method for the carrier 20 in FIG. 24 is identical to the manufacturing method for the carrier 20 in FIG. 3. In the manufacturing method for this carrier 20, the linking portions 27 b are cut off of the formed workpiece 20 to form the pronged annular member 20 d with an inner wall portion shown in FIG. 25 (step S410), the inner diameter of the prong portions 26 d of the formed pronged annular member 20 d with the inner wall portion is widened (step S420), trimming of the cross-section (the side surface of the bottom portion 22 d ) that was cut off when the pronged annular member 20 d with an inner wall portion was formed is carried out (step S425), the trimming of the side surface of the prong portions 26 d of the pronged annular member 20 d with an inner wall portion is carried out (step S430), the metallic soap that was coated onto the surface of the pronged annular member 20 d with an inner wall portion is removed (step S440), the pronged annular member 20 c shown in FIG. 13 to FIG. 15 described above is formed by cutting the portion that includes the inner wall portion 24 d off from the pronged annular member 20 d with an inner wall portion (step S445), coining that adjusts the roughness or evenness of the surface of the bottom portion 22 c is carried out (step S450), and the carrier 20 is thereby completed. In this modified example of the manufacturing method for the carrier 20 as well, because the workpiece 20 b is formed by one press process being carried out on the prepared annular base material 20 a, similar to the manufacturing method for the carrier 20 in the embodiment, it is not necessary to carry out annealing in the steps for completing the carrier 20 from the base material 20 a. As a result, it is possible to reduce the steps for manufacturing the carrier 20 from the base material 20 a, and it is possible to shorten the time for manufacturing the carrier 20 from the base material 20 a. In addition, similar to the manufacturing method for the carrier 20 in the embodiment, because the workpiece 20 b is formed from the base material 20 a by cold forging, the time that is necessary for heating the base material 20 a, and cooling the formed workpiece 20 b, and the like becomes unnecessary. As a result, it is possible to further shorten the time for completing the carrier 20 from the base material 20 a.

In the manufacturing method for the carrier 20 of the embodiment, the linking portions 27 b and the portion that includes the inner wall portion 24 b are cut off of the workpiece 20 b. However, only the linking portions 27 b may be cut off without cutting off the portion that includes the inner wall portion 24 b.

In the manufacturing method for the carrier 20 of the embodiment, when the workpiece 20 b is formed by one press process, as shown in FIG. 5 to FIG. 7 described above, the workpiece 20 b is formed such that the inner circumferential surfaces of the inner wall portion 24 b and the boss portion 28 are continuously curved surfaces, but the workpiece 20 b may be formed such that the inner circumferential surface of the inner wall portion 24 b and the boss portion 28 b acquire a predetermined form (for example, a spline shape, a serrated shape, or the like). An example of a lower die 50 b of the process apparatus 40B that is used when the inner circumferential surface of the inner wall portion 24 b is made a spline shape is shown in FIG. 26, and an example of the workpiece 120 b that is formed by this process apparatus 40B is shown in FIG. 27 to FIG. 29. In FIG. 26, the lower die mandrel 51 b of the lower die 50 b of the process apparatus 40B is one in which the shape (the shape of the portion of the lower die mandrel 51 that is used in the formation of the inner wall portion 24 b of the workpiece 20 b ) from the upper end portion of the lower die mandrel 51 (refer to FIG. 8) described above to a position that is a distance L1 below the upper end portion thereof is modified into a spline shape. Note that, except for the point that the shape of the lower die mandrel 51b is different, the process apparatus 40B is identical to the process apparatus 40 described above. In addition, FIG. 27 is a perspective view of the external appearance of the workpiece 120 b of the modified example, FIG. 28 is an AA perspective view in which the workpiece 120 b in FIG. 27 is viewed from the A-A plane, and FIG. 29 is a BB perspective view in which the workpiece 120 b in FIG. 27 is viewed from the B-B plane. In FIG. 27 to 29, except for the point that the inner circumferential surface of the inner wall portion 124 b has a spline shape, the workpiece 120 b has a shape that is identical to that of the workpiece 20 b in FIG. 5 to FIG. 7, and thus the parts formed with an identical shape are denoted by identical reference numerals. By forming a workpiece 120 b using a process apparatus 40B that has such a lower die mandrel 51b, when the inner wall portion 124 b is formed by the press process, because the sealed state of the base material 20 a on the inner circumference side of the inner wall portion 124 b is relaxed, the base material 20 a readily flows toward the inner wall portion 124 b side, and it is possible to reduce further the load that is necessary when carrying out the press process. Furthermore, by making the inner circumferential surface of the inner wall portion 124 b into a spline shape when carrying out one press process in this manner, when it is necessary to make the inner circumferential surface of the inner wall portion 24 into a spline shape while manufacturing the carrier 20, it is not necessary to provide a step in which the inner circumferential surface of the inner wall portion 24 b is formed into a spline shape after the press process, and it is possible to shorten further the time for completing the carrier 20 from the base material 20 a. In this modified example, the inner circumferential surface of the inner wall portion 124 b is made into a spline shape. However, this spline shape is not limiting, and if the sealed condition of the base material 20 a on the inner circumference side of the inner wall portion 24 b (124 b ) is relaxed while the press process is being carried out and the base material 20 a is a shape that readily flows toward the inner wall portion 24 b side, then, for example, the inner circumferential surface of the inner wall portion 24 b may be one that has a concavo-convex shape or the like.

In the manufacturing method for the carrier 20 of the embodiment, the step after the base material 20 a has been prepared is carried out by cold forging. However, this is not limiting, and the steps after the base material 20 a has been prepared may be carried out by warm forging, hot forging, or the like.

In the manufacturing method for the carrier 20 of the embodiment, annealing is carried out in the step after the base material 20 a has been prepared, but annealing does not need to be carried out.

In the manufacturing method for the carrier 20 of the embodiment, the outer wall portion 25 b is formed such that the thickness D1 of the prong portions 26 b of the workpiece 20 b is thicker than the thickness D2 of the linking portions 27 b. However, the outer wall portion 25 b may be formed such that the thickness D1 of the prong portions 26 b is substantially identical to the thickness D2 of the linking portions 27 b, and the outer wall portion 25 may be formed such that the thickness D1 of the prong portions 26 b is slightly thinner than the thickness D2 of the linking portions 27 b.

In the manufacturing method for the carrier 20 of the embodiment, the workpiece 20 b is formed such that the thickness D2 of the linking portions 27 b along the inner circumference of the linking portions 27 b is substantially even. However, the workpiece 20 b may be formed such that the thickness of the linking portions 227 b becomes larger as the distance from the prong portions 26 b becomes larger, that is, becomes larger toward the center of the linking portions 27 b along the inner circumference of the linking portions 27 b. FIG. 30 is a perspective view of the external appearance of the workpiece 220 b that is formed in this case, FIG. 31 is an AA perspective view in which the workpiece 220 b in FIG. 30 is viewed from the A-A plane, and FIG. 32 is a BB perspective view in which the workpiece 220 b in FIG. 30 is viewed from the B-B plane. In FIG. 3 1, “D21” denotes a thickness that corresponds to the thickness D2 ((R8-R7)/2) of the linking portions 27 b of the workpiece 20 b of the embodiment, and “D22” denotes a thickness that is thicker than the thickness D21. In FIG. 30 to FIG. 32, except for the point that the shape (thickness) of the linking portions 227 b and the shape of the end portion of the inner wall portion 224 b are different, the workpiece 220 b is formed having a shape that is identical to that of the workpiece 20 b in FIG. 5 to FIG. 7, and thus, identical reference numerals denote portions that have an identical shape. Here, the case in which the workpiece 20 b and the workpiece 220 b are formed by the press process will be considered. In this case, as shown in FIG. 11 described above, in the embodiment, the outer wall portion 25 b, which includes the prong portions 26 b and the linking portions 227 b, is formed by the upper die punch 43 and the second die 54, the boss portion 28 b is formed by the lower die mandrel 51, the lower die punch 52, and the first die 53, and the inner wall portion 24 b is formed by the lower die mandrel 51 and the upper die punch 43. At this time, because the lower die punch 52 is disposed on the end portion (the lower end portion of the boss portion 28 b in FIG. 7) of the boss portion 28 b, the elongation of the boss portion 28 b toward the end portion side thereof due to the lower die punch 52 is limited, and the length from the bottom portion 22 b to the end portion of the boss portion 28 b is substantially constant along the circumference of the boss portion 28 b. However, the end portion (the upper end portion of the inner wall portion 24 b in FIG. 7) of the inner wall portion 24 b becomes free, and the elongation of the inner wall portion 24 b toward the end portion side is not limited. Additionally, because the base material 20 a flows readily, the length from the bottom portion 22 b to the end portion of the inner wall portion 24 b is not constant along the circumference of the inner wall portion 24 b, and thus the end portion of the inner wall portion 24 b may be formed into in an irregular wavy shape. Generally, the base material 20 a flows toward the inner wall portion 24 b more readily as the thickness of the outer wall portion 25 b increases. In other words, as in the embodiment, the base material 20 a flows more readily in the inner wall portion 28 at a position that is opposed to the prong portions 26 b than at a position opposed to the linking portions 27 b, when the thickness D1 of the prong portions 26 a is thicker than the thickness D2 of the linking portions 27 b and the thickness of the prong portions 26 b and the linking portions 27 b is substantially constant along the outer circumference of the bottom portion 22 b. Therefore, in the inner wall portion 24 b, the length from the bottom portion 22 b at a position that is opposed to the prong portions 26 b to the end portions readily becomes longer than the length from the bottom portion 22 b at a position that is opposed to the linking portions 27 b to the end portion. As a result, the end portion of the inner wall portion 24 b readily acquires an irregular wavy shape. In particular, in the inner wall portion 24 b, at a position that is opposed to the approximate center of the linking portions 27 b along the inner circumference (the outer circumference of the bottom portion 22 b ) of the linking portions 27 b, the distance from the prong portions 26 b becomes larger, and therefore the base material 20 a flows with more difficulty. As a result, the length from the bottom portion 22 b to the end portion of the inner wall portion 24 b readily becomes short. In contrast, as shown in FIGS. 30 to 32, in the inner wall portion 224 b, variations in the ease of the flow of the base material 20 b due to the base material 20 a readily flowing at positions that are opposed to the linking portions 227 b are suppressed if the linking portions 227 b are formed such that the distance from the prong portions 22 b is larger, that is, the thickness from the thickness D21 to the thickness D22 becomes larger from the end portion side toward the center of the linking portions 227 b along the inner circumference of the linking portions 227 b, or in other words, if the press process is carried out by using a process apparatus (not illustrated) having a second die (not illustrated) formed so that such linking portions 227 b are formed instead of the second die 54 of the process apparatus 40. Thereby, it is possible to suppress significant variations in the length from the bottom portion 22 b to the end portion of the inner wall portion 224 b along the circumference of the inner wall portion 224 b, and it is possible to suppress the end portion of the inner wall portion 224 b from acquiring an irregular wavy shape. In this modified example, it is possible to suppress the end portion of the inner wall portion 224 b from acquiring an irregular wavy shape by forming the linking portions 227 b such that the thickness from the thickness D21 to the thickness D22 becomes larger from the end portion side toward the center of the linking portions 227 b along the inner circumference of the linking portions 227 b. However, this is not limiting, and the length from the bottom portion 22 b to the end portion of the inner wall portion 24 b (224 b ) may be adjusted by varying the thickness of the linking portions 27 b (227 b ) according to the distance from the prong portions 26 b.

In the manufacturing method for the carrier 20 of the embodiment, when the workpiece 20 b is formed by using the process apparatus 40, the length from the bottom portion 22 b to the end portion of the boss portion 28 b is limited by using the lower die punch 52. However, instead of or in addition to this, the length from the bottom portion 22 b to the end portion of the inner wall portion 24 b may be limited by using a member that limits the elongation of the inner wall portion 24 b toward the end portion. In addition, the workpiece 20 b may be one in which neither the length from the bottom portion 22 b to the end portion of the boss portion 28 b nor the length from the bottom portion 22 b to the end portion inner wall portion 24 b are limited. Below, the case will be explained in which, a member that limits the elongation of the inner wall portion 24 b toward the end portion side is used instead of the lower die punch 52. In this case, contrary to the case in which the base material 20 a is elongated at the end portion side of the inner wall portion 24 b, the base material 20 a flows more readily toward the boss portion 28 b as the thickness of the outer wall portion 25 b decreases. That is, in the inner wall portion 28 b, the base material 20 a flows more readily to positions that are opposed to the linking portions 27 b than positions that are opposed to the prong portions 26 b when, similar to the embodiment, the thickness D1 of the prong portions 26 b is thicker than the thickness D2 of the linking portions 27 b and the thickness of the prong portions 26 b and the linking portions 27 b is substantially constant along the outer circumference of the bottom portion 22 b. Therefore, the end portion of the boss portion 28 b readily forms an irregular wavy shape. In particular, at a position that is opposed to the approximate center of the linking portions 27 b along the inner circumference of the linking portions 27 b, because the distance from the prong portions 26 b is large and the base material 20 a flows readily, the distance from the bottom portion 22 b to the end portion of the boss portion 28 b readily becomes long. In contrast, similar to the content shown in FIG. 30 to FIG. 32, variations in the ease of the flow of the base material 20 b due to the base material 20 a flowing with difficulty at positions that are opposed to the linking portions 227 b in the boss portion 28 b are suppressed if the linking portions 227 b are formed such that as the distance from the prong portions 22 b increases, that is, as the thickness from the thickness D21 to the thickness D22 increases from the end portion side toward the center of the linking portions 227 b along the inner circumference of the linking portions 227 b, or in other words, if the press process is carried out by using a process apparatus (not illustrated) having a second die (not illustrated) formed so that such linking portions 227 b are formed instead of the second die 54 of the process apparatus 40. Thereby, it is possible to suppress significant variations in the length from the bottom portion 22 b to the end portion of the boss portion 28 b along the circumference of the boss portion 28 b, and it is possible to suppress the end portion of the boss portion 28 b from acquiring an irregular wavy shape. In this modified example, it is possible to suppress the end portion of the boss portion 28 b from acquiring an irregular wavy shape by forming the linking portions 227 b such that the thickness from the thickness D21 to the thickness D22 increases from the end portion side toward the center of the linking portions 227 b along the inner circumference of the linking portions 227 b. However, this is not limiting, and the length from the bottom portion 22 b to the end portion of the boss portion 28 b may be adjusted by varying the thickness of the linking portions 227 b according to the distance from the prong portions 26 b.

In the manufacturing method for the carrier 20 in the embodiment, the outer wall portion 25 b is formed such that the outer diameter R6 of the prong portions 26 b and the inner diameter R7 of the linking portions 27 b of the workpiece 20 b are substantially identical, but the outer wall portion 25 b may be formed such that one among the outer diameter R6 of the prong portions 26 b and the inner diameter R7 of the linking portions 27 b is slightly larger than the other.

In the manufacturing method for the carrier 20 of the embodiment, a workpiece 20 b was formed that includes a circular bottom portion 22 b having a hole 23 b in the center thereof and an inner wall portion 24 b around the hole 23 b, but the bottom portion 22 b may be formed without the inner wall portion 24 b around the hole 23 b.

In the manufacturing method for the carrier 20 of the embodiment, the linking portions 27 b are removed from the workpiece 20 b by applying a force in a direction from the base side of the linking portions 27 b of the workpiece 20 b at the bottom portion 22 b toward the linking portions 27 b, but the linking portions 27 b may be removed from the workpiece 20 b by another method, such as applying a force in a direction from the inside of the linking portions 27 b (the inside of the outer wall portion 25 b ) toward the outside. In this case, the outer wall portion 25 b may be formed such that the outer diameter R8 of the linking portions 27 b is substantially identical to the outer diameter R6 of the prong portions 26 b.

In the manufacturing method for the carrier 20 of the embodiment, after forming the pronged annular member 20 c by cutting the linking portions 27 b off of the workpiece 20 b, the inner diameter of the prong portions 26 b of the pronged annular member 20 c is widened, trimming of the side surface of the prong portions 26 c is carried out, the metallic soap that has been coated onto the surface is removed, and coining is carried out to adjust the roughness or evenness of the surface of the bottom portion 22 c. However, among these steps, one or a plurality of the steps may be omitted.

In the manufacturing method for the carrier 20 of the embodiment, the carrier 20 includes a circular bottom portion 22 having a hole 23 formed in the center thereof, prong portions 26 that include four prongs that are formed on the circumference of the bottom portion 22 substantially perpendicular to the bottom portion 22, and a boss portion 28 that is formed as a hollow shaft-shaped cylinder on the side of the bottom portion 22 that is opposed to the prong portions 26. However, the boss portion 28 may be omitted.

In the embodiment, a manufacturing method for a carrier 20 for a planetary gear mechanism was explained. However, the embodiment is not limited to the case in which a carrier 20 for a planetary gear mechanism is manufactured, and may be applied to a manufacturing method for any type of pronged annular member if the pronged annular member has an annular-shaped annular member and at least one prong formed substantially perpendicular on the outer circumference of this annular-shaped annular member.

Above, the embodiment of a preferred mode for implementing the present invention was explained. However, the present invention is not limited in any manner by such embodiments, and of course various modifications are possible that do not depart from the spirit of the present invention.

INDUSTRIAL APPLICABILITY

The present invention can be used in industries that manufacture pronged annular members such as the carrier for a planetary gear mechanism. 

1. A manufacturing method for an annular member that manufactures an annular member that comprises an annular-shaped annular member and at least one prong formed substantially perpendicular on the outer circumference of this annular member, wherein: (a) an annular base material is prepared; (b) a workpiece is formed by one press process applied to this base material, the workpiece including a circular bottom portion having a hole in the center thereof and a skirt-shaped outer wall portion that comprises prong portions that form prongs on the outer circumference of this bottom portion and linking portions that link these prong portions; and (c) a pronged annular member is formed by removing the linking portions from the formed workpiece.
 2. The manufacturing method for an annular member according to claim 1, characterized in that at least the steps (b) and after are carried out by using cold forging.
 3. The manufacturing method for an annular member according to claim 1, characterized in that at least the steps (b) and after do not carry out annealing.
 4. The manufacturing method for an annular member according to claim 1, wherein: the step (b) is a step in which the workpiece is formed such that the outer diameter of the linking portions in the outer wall portion is larger than the outer diameter of the prong portions; and the step (c) is a step that comprises a step (c1) in which the linking portions are removed such that the linking portions in the outer wall portion are sheared off by a force that is applied in a direction from the prong portions towards the prongs.
 5. The manufacturing method for an annular member according to claim 4, wherein the step (b) is a step in which the workpiece is formed such that the inner diameter of the linking portions in the outer wall portion is larger than the inner diameter of the prong portions.
 6. The manufacturing method for an annular member according to claim 4, wherein the step (b) is a step in which the workpiece is formed such that the inner diameter of the linking portions in the outer wall portion is substantially identical to the outer diameter of the prong portions.
 7. The manufacturing method for an annular member according to claim 4, wherein the step (c1) is a step in which the linking portions are removed and the portion of the workpiece that includes the hole in the bottom portion is cut off.
 8. The manufacturing method for an annular member according to claim 1, wherein the step (b) is a step in which the workpiece is formed such that the wall thickness of connecting portions, which are the portions that connect the prong portions and the linking portions, is thinner than the wall thickness of the prong portions and the wall thickness of the linking portions.
 9. The manufacturing method for an annular member according to claim 1, wherein the step (b) is a step in which the workpiece is formed such that the wall thickness of the linking portions is thinner than the wall thickness of the prong portions.
 10. The manufacturing method for an annular member according to claim 1, wherein the step (b) is a step in which the workpiece is formed such that the base of the inside of the prong portions at the bottom portion has a wall thickness through the radius that is larger in comparison to the base of the inside of the linking portions at the bottom portion.
 11. The manufacturing method for an annular member according to claim 1, wherein the step (c) is a step that comprises a step (c2), in which the inner diameter of the prong portions is widened after the linking portions have been removed from the formed workpiece.
 12. The manufacturing method for an annular member according to claim 1, wherein the step (c) is a step that comprises a step (c3), in which the trimming of the locations that link the prong portions and the linking portions is carried out after the linking portions have been removed from the formed workpiece.
 13. The manufacturing method for an annular member according to claim 1, wherein the step (c) is a step that comprises a step (c4), in which one of at least the roughness and the evenness of the surface of at least the inside of the bottom portion are adjusted after the linking portions have been removed from the formed workpiece.
 14. The manufacturing method for an annular member according to claim 13, wherein: the step (a) is a step in which a base material is prepared whose surface has been subject to a phosphating treatment that provides a surface coating that includes a metallic soap; and the step (c4) is a step in which at least one of the roughness and the evenness of the surface is adjusted after providing a treatment that removes the metallic soap.
 15. The manufacturing method for an annular member according to claim 1, wherein the step (b) is a step in which the workpiece is formed that has a cylindrical vertical wall portion that is concentric to the outer wall portion around the hole in the center of the bottom portion.
 16. The manufacturing method for an annular member according to claim 15, wherein the step (b) is a step in which the workpiece is formed such that the length up to the end portion of the vertical wall portion is adjusted by varying the wall thickness of the linking portions according to the distance from the prong portions.
 17. The manufacturing method for an annular member according to claim 16, wherein the step (b) is a step in which a workpiece is formed such that the wall thickness of the linking portions becomes continuously larger as the distance from the prong portions becomes larger.
 18. The manufacturing method for an annular member according to claim 15, wherein the step (b) is a step in which a workpiece is formed such that the inner circumferential surface of the vertical wall portion has a predetermined shape.
 19. The manufacturing method for an annular member according to claim 18, wherein the step (b) is a step in which a workpiece is formed such that the predetermined shape is a spline shape.
 20. The manufacturing method for an annular member according to claim 15, wherein the step (b) is a step in which the workpiece is formed having vertical wall portions that comprise a first vertical wall portion that is disposed in a direction identical to that of the outer wall portion with respect to the hole in the center of the bottom portion and a second vertical wall portion that is disposed in a direction that is opposed to that of the outer wall portion with respect to the hole in the center of the bottom portion.
 21. The manufacturing method for an annular member according to claim 20, wherein the step (c) is a step that comprises a step (c5), in which the first vertical wall portion is removed from the workpiece after the linking portions have been removed from the formed workpiece.
 22. The manufacturing method for an annular member according to claim 1, wherein the annular member is a carrier in a planetary gear mechanism.
 23. A pronged annular member that comprises an annular-shaped annular member and at least one prong formed substantially perpendicular on the outer circumference of the annular member, wherein: the pronged annular member is formed by removing the linking portions from a workpiece that is formed by one press process applied to an annular base material, the workpiece including a circular bottom portion that has a hole in the center thereof and a skirt-shaped outer wall portion that comprises prong portions that form prongs on the outer circumference of the bottom portion and linking portions that link the prong portions.
 24. The pronged annular member according to claim 23, wherein: the workpiece is formed such that the outer diameter of the linking portions in the outer wall portion is larger than the outer diameter of the prong portions; and the pronged annular member is formed by removing the linking portions such that the linking portions in the outer wall portion are sheared off by a force that is applied in a direction from the prong portions toward the prongs.
 25. The pronged annular member according to claim 24, wherein the workpiece is formed such that the inner diameter of the linking portions in the outer wall portion is larger than the inner diameter of the prong portions.
 26. The pronged annular member according to claim 24, wherein the workpiece is formed such that the inner diameter of the linking portions in the outer wall portion is substantially identical to that of the outer diameter of the prong portions.
 27. The pronged annular member according to claim 23, wherein the pronged annular member is formed by removing the linking portions and cutting off the portion of the workpiece that includes the hole in the bottom portion.
 28. The pronged annular member according to claim 23, wherein the workpiece is formed such that the wall thickness of the connecting portions, which are the portions that connect the prong portions and the linking portions, are thinner than the wall thickness of the prong portions and the wall thickness of the linking portions.
 29. The pronged annular member according to claim 23, wherein the workpiece is formed such that the wall thickness of the linking portions is thinner than the wall thickness of the prong portions.
 30. The pronged annular member according to claim 23, wherein the workpiece is formed such that the base of the inside of the prong portions at the bottom portion has a wall thickness across the radius that is larger in comparison the base of the inside of the linking portions at the bottom portion.
 31. The pronged annular member according to claim 23, wherein the pronged annular member is formed such that the inner diameter of the prong portions is widened after the linking portions have been removed from the formed workpiece.
 32. The pronged annular member according to claim 23, wherein the pronged annular member is formed by carrying out trimming of the locations that link the prong portions and the linking portions after the linking portions have been removed from the formed workpiece.
 33. The pronged annular member according to claim 23, wherein the pronged annular member is formed by adjusting at least one of the roughness and the evenness of at least the inside surface of the bottom portion after the linking portions have been removed from the formed workpiece.
 34. The pronged annular member according to claim 33, wherein: the annular base material is a base material on which a phosphating treatment that provides a surface coating that includes a metallic soap has been carried out on the surface thereof; and the pronged annular member is formed by adjusting at least one of the roughness and the evenness of the surface after providing a treatment that removes the metallic soap.
 35. The pronged annular member according to claim 23, wherein the workpiece is a member that has a cylindrical vertical wall portion that is concentric to the outer wall portion along the hole in the center of the bottom portion.
 36. The pronged annular member according to claim 35, wherein the workpiece is formed by adjusting the length to the end portion of the vertical wall portion by varying the wall thickness of the linking portions according to the distance from the prong portions.
 37. The pronged annular member according to claim 36, wherein the workpiece is formed such that the wall thickness of the linking portions becomes continuously larger as the distance from the prong portions becomes larger.
 38. The pronged annular member according to claim 35, wherein the workpiece is formed such that the inner circumferential surface of the vertical wall portions has a predetermined shape.
 39. The pronged annular member according to claim 38, wherein the workpiece is formed such that the inner circumferential surface of the vertical wall portions has a spline shape.
 40. The pronged annular member according to claim 35, wherein the workpiece has vertical wall portions formed thereon, the vertical wall portions including a first vertical wall portion having a direction that is identical to that of the outer wall portion with respect to the hole in the center of the bottom portion and a second vertical wall portion having a direction that is opposed to that of the outer wall portion with respect to the hole in the center of the bottom portion.
 41. The pronged annular member according to claim 40, wherein the pronged annular member is formed by removing the first vertical wall portion from the workpiece after the linking portions have been removed from the formed workpiece.
 42. The pronged annular member according to claim 23, wherein the pronged annular member is a carrier in a planetary gear mechanism. 